Ms 260 Pro, How Does It Sound?

[Canyon Angler]

Sounds slightly lean to me.

Me too at WOT. Better to run it a little rich until it breaks in than to burn it up right out of the gate with it too lean.

ETA: Just saw "Take 2" ... sounds a little better (richer) at WOT.

 

[SteveSr]

Tom,

What carburetor do you have on this saw? Walbro # or is it aftermarket?

If it is OEM the only thing that I can really add is that Stihl "calibrates" their OEM carburetors such that the saw should pretty much, except for a minor touch-up, run pretty good at the stock settings. This has been my experience with this same model of saw and Stihl saws in general. Stihl calibrates these for 72 degrees F and at or near sea level. If the saw doesn't run or runs extremely badly at the stock carb settings there is usually something wrong with either the saw or the carb.

You may want to go back to initial carb settings and see how it runs.

You mentioned "o"-rings on the adjustment screws. The main reasons for these is to prevent very small air seepage around the screw upsetting the mixture. In the states this was added for EPA compliance on some carb models.

 

[Vintage Engine Repairs]

Tom,

What carburetor do you have on this saw? Walbro # or is it aftermarket?

If it is OEM the only thing that I can really add is that Stihl "calibrates" their OEM carburetors such that the saw should pretty much, except for a minor touch-up, run pretty good at the stock settings. This has been my experience with this same model of saw and Stihl saws in general. Stihl calibrates these for 72 degrees F and at or near sea level. If the saw doesn't run or runs extremely badly at the stock carb settings there is usually something wrong with either the saw or the carb.

You may want to go back to initial carb settings and see how it runs.

You mentioned "o"-rings on the adjustment screws. The main reasons for these is to prevent very small air seepage around the screw upsetting the mixture. In the states this was added for EPA compliance on some carb models.

Wow thanks for all that info! It’s a genuine walbro I think I was able to clear the blocked idle hole after some great advice on here! I’ll get it into some wood and video it again!

 

[SteveSr]

Wow thanks for all that info! It’s a genuine walbro I think I was able to clear the blocked idle hole after some great advice on here! I’ll get it into some wood and video it again!

Which Walbro model? Should be stamped on the carb like WT-426, WT-403, WTE-1, etc. Stihl used so many different Walbro carbs on this saw over the years (and regions) that I lost count.

 

[Vintage Engine Repairs]

Which Walbro model? Should be stamped on the carb like WT-426, WT-403, WTE-1, etc. Stihl used so many different Walbro carbs on this saw over the years (and regions) that I lost count.

This is a WT 426

 

[SteveSr]

This is a WT 426

The WT-426 is what is known as a "limited range" fully adjustable carb. With these types of carbs most of the L & H speed mixture goes through fixed jets with a smaller amount bypassing and going through the screws. The advantage is that the adjustments are not nearly as "fiddly" as carbs like the WT-194 where the whole mixture goes through the needles. The down side is that if the saw has been modified or something is not "right" the needle settings might seem extreme.

Like most carbs the total mixture that is fed to the engine at high speed (WOT) is a combination of the flow through BOTH L & H circuits. So the "L" screw setting can affect the "H" setting somewhat. The "H" setting can't affect the "L" as the main nozzle check valve is closed at idle.

Because of this it is best to get the "L" set correctly and then move onto the "H" setting. Keep in mind that the optimum settings are dependent on both altitude and temperature. Altitude lowers air density and makes the mixture richer while colder "winter" temperatures increases air density and leans out the mixture. If you tune the saw at 90 degrees F it will likely be too lean by winter when the temps drop.

I believe that the stock settings for this carb are L=1T; H=1T. It was originally introduced for the 026 / 026Pro which is the predecessor and basically the same as the MS260 with perhaps some muffler cover changes.

Just for curiosity, what does the inside of the muffler cover look like (post a photo) and have you modified it?

 

[Vintage Engine Repairs]

The WT-426 is what is known as a "limited range" fully adjustable carb. With these types of carbs most of the L & H speed mixture goes through fixed jets with a smaller amount bypassing and going through the screws. The advantage is that the adjustments are not nearly as "fiddly" as carbs like the WT-194 where the whole mixture goes through the needles. The down side is that if the saw has been modified or something is not "right" the needle settings might seem extreme.

Like most carbs the total mixture that is fed to the engine at high speed (WOT) is a combination of the flow through BOTH L & H circuits. So the "L" screw setting can affect the "H" setting somewhat. The "H" setting can't affect the "L" as the main nozzle check valve is closed at idle.

Because of this it is best to get the "L" set correctly and then move onto the "H" setting. Keep in mind that the optimum settings are dependent on both altitude and temperature. Altitude lowers air density and makes the mixture richer while colder "winter" temperatures increases air density and leans out the mixture. If you tune the saw at 90 degrees F it will likely be too lean by winter when the temps drop.

I believe that the stock settings for this carb are L=1T; H=1T. It was originally introduced for the 026 / 026Pro which is the predecessor and basically the same as the MS260 with perhaps some muffler cover changes.

Just for curiosity, what does the inside of the muffler cover look like (post a photo) and have you modified it?

Lots of awesome and valuable info there mate!! Thank you very much!

The muffler is stock (and cane standard without a spark arrester screen for Uk matket). I’ll take some photos later warmest regards and thanks again!!